A nonequilibrium thermodynamic approach to biological energy conversion systems

Energy conversion devices are commonly built from individual subunits in order to increase the force or flow that can be obtained from the device. Examples occur in both engineering and biology and include the cylinders of an internal combustion engine, the plates of a battery, the cross-bridges of muscle, and the active transport complexes in a cell membrane;This work describes the behavior of assemblies of individual energy converting subunits. The linear phenomenological laws of nonequilibrium thermodynamics are used as constitutional equations that describe the relationship between the forces and flows of a subunit. These relationships along with the restrictions imposed because of the organization of the system are used to derive equations relating the overall flows and forces. Two types of systems have been considered where the total input flow is the sum of the individual input flows, and the output flow is either also the sum of the subunit flows or is the same as each subunit flow. Most of the effort has been directed toward describing systems in which the subunits are not all phenomenologically identical and the fractions of subunit types vary. Systems containing two distinct types of subunit have been studied. Several properties are investigated, including limiting operating states and the input flows needed to support these states. An overall coupling coefficient is derived that represents an effectiveness factor for the system. More complex systems are briefly discussed;As an example, muscle contraction has been considered as a system where the output flow is the same for each subunit. Unfortunately, because it is not yet possible to measure the number of active subunits in muscle, applications of the theory is limited to describing properties that do not depend on the number of subunits. These include the maximum contraction velocity, the isometric rate of adenosine triphosphate hydrolysis, and the system coupling. The theory is applied to phosphorylation, calcium binding and isoenzymes variations that have been found to affect the mechanical and chemical properties of muscle

Predator decline leads to decreased stability in a coastal fish community

Fisheries exploitation has caused widespread declines in marine predators. Theory predicts that predator depletion will destabilise lower trophic levels, making natural communities more vulnerable to environmental perturbations. However, empirical evidence has been limited. Using a community matrix model, we empirically assessed trends in the stability of a multispecies coastal fish community over the course of predator depletion. Three indices of community stability (resistance, resilience and reactivity) revealed significantly decreasing stability concurrent with declining predator abundance. The trophically downgraded community exhibited weaker top-down control, leading to predator-release processes in lower trophic levels and increased susceptibility to perturbation. At the community level, our results suggest that high predator abundance acts as a stabilising force to the naturally stochastic and highly autocorrelated dynamics in low trophic species. These findings have important implications for the conservation and management of predators in marine ecosystems and provide empirical support for the theory of predatory control

Visitation to Cottonseed Storage Sites by Feral Swine and Evidence of Gossypol Exposure

Texas ranks first in U.S. cotton production, and southern Texas is a major region of production within the state. Within Kleberg County, for example, approximately 16,147 ha are planted in cotton annually, yielding approximately 68,200 bales, or 15,467 metric tons, of cotton (U.S. Department of Agriculture [USDA] 2009). Cotton producers have discovered new uses for cotton ginned by-products, such as hydro-mulch (Holt et al. 2005) used as a protein supplement for range livestock (DelCurto et al. 2000) and white-tailed deer (Odocoileus virginianus; Cooper 2006). Because of this, much of the materials are temporarily stored for later use

Predator decline leads to decreased stability in a coastal fish community

Abstract Fisheries exploitation has caused widespread declines in marine predators. Theory predicts that predator depletion will destabilise lower trophic levels, making natural communities more vulnerable to environmental perturbations. However, empirical evidence has been limited. Using a community matrix model, we empirically assessed trends in the stability of a multispecies coastal fish community over the course of predator depletion. Three indices of community stability (resistance, resilience and reactivity) revealed significantly decreasing stability concurrent with declining predator abundance. The trophically downgraded community exhibited weaker top-down control, leading to predator-release processes in lower trophic levels and increased susceptibility to perturbation. At the community level, our results suggest that high predator abundance acts as a stabilising force to the naturally stochastic and highly autocorrelated dynamics in low trophic species. These findings have important implications for the conservation and management of predators in marine ecosystems and provide empirical support for the theory of predatory control

Production of tocotrienols in seeds of cotton (Gossypium hirsutum L.) enhances oxidative stability and offers nutraceutical potential

Upland cotton (Gossypium hirsutum L.) is an economically important multi-purpose crop cultivated globally for fibre, seed oil and protein. Cottonseed oil also is naturally rich in vitamin E components (collectively known as tocochromanols), with a- and c-tocopherols comprising nearly all of the vitamin E components. By contrast, cottonseeds have little or no tocotrienols, tocochromanols with a wide range of health benefits. Here, we generated transgenic cotton lines expressing the barley (Hordeum vulgare) homogentisate geranylgeranyl transferase coding sequence under the control of the Brassica napus seed-specific promoter, napin. Transgenic cottonseeds had ~twofold to threefold increases in the accumulation of total vitamin E (tocopherols + tocotrienols), with more than 60% c-tocotrienol. Matrix assisted laser desorption ionization-mass spectrometry imaging showed that c-tocotrienol was localized throughout the transgenic embryos. In contrast, the native tocopherols were distributed unequally in both transgenic and non-transgenic embryos. a- Tocopherol was restricted mostly to cotyledon tissues and c-tocopherol was more enriched in the embryonic axis tissues. Production of tocotrienols in cotton embryos had no negative impact on plant performance or yield of other important seed constituents including fibre, oil and protein. Advanced generations of two transgenic events were field grown, and extracts of transgenic seeds showed increased antioxidant activity relative to extracts from non-transgenic seeds. Furthermore, refined cottonseed oil from the two transgenic events showed 30% improvement in oxidative stability relative to the non-transgenic cottonseed oil. Taken together, these materials may provide new opportunities for cottonseed co-products with enhanced vitamin E profile for improved shelf life and nutrition

Effect of d-cycloserine on fear extinction training in adults with social anxiety disorder

© 2019 Hofmann et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Preclinical and clinical data have shown that D-cycloserine (DCS), a partial agonist at the N-methyl-d-aspartate receptor complex, augments the retention of fear extinction in animals and the therapeutic learning from exposure therapy in humans. However, studies with nonclinical human samples in de novo fear conditioning paradigms have demonstrated minimal to no benefit of DCS. The aim of this study was to evaluate the effects of DCS on the retention of extinction learning following de novo fear conditioning in a clinical sample. Eighty-one patients with social anxiety disorder were recruited and underwent a previously validated de novo fear conditioning and extinction paradigm over the course of three days. Of those, only 43 (53%) provided analyzable data. During conditioning on Day 1, participants viewed images of differently colored lamps, two of which were followed by with electric shock (CS+) and a third which was not (CS-). On Day 2, participants were randomly assigned to receive either 50 mg DCS or placebo, administered in a double-blind manner 1 hour prior to extinction training with a single CS+ in a distinct context. Day 3 consisted of tests of extinction recall and renewal. The primary outcome was skin conductance response to conditioned stimuli, and shock expectancy ratings were examined as a secondary outcome. Results showed greater skin conductance and expectancy ratings in response to the CS+ compared to CS- at the end of conditioning. As expected, this difference was no longer present at the end of extinction training, but returned at early recall and renewal phases on Day 3, showing evidence of return of fear. In contrast to hypotheses, DCS had no moderating influence on skin conductance response or expectancy of shock during recall or renewal phases. We did not find evidence of an effect of DCS on the retention of extinction learning in humans in this fear conditioning and extinction paradigm

Culture Enriched Molecular Profiling of the Cystic Fibrosis Airway Microbiome

The microbiome of the respiratory tract, including the nasopharyngeal and oropharyngeal microbiota, is a dynamic community of microorganisms that is highly diverse. The cystic fibrosis (CF) airway microbiome refers to the polymicrobial communities present in the lower airways of CF patients. It is comprised of chronic opportunistic pathogens (such as Pseudomonas aeruginosa) and a variety of organisms derived mostly from the normal microbiota of the upper respiratory tract. The complexity of these communities has been inferred primarily from culture independent molecular profiling. As with most microbial communities it is generally assumed that most of the organisms present are not readily cultured. Our culture collection generated using more extensive cultivation approaches, reveals a more complex microbial community than that obtained by conventional CF culture methods. To directly evaluate the cultivability of the airway microbiome, we examined six samples in depth using culture-enriched molecular profiling which combines culture-based methods with the molecular profiling methods of terminal restriction fragment length polymorphisms and 16S rRNA gene sequencing. We demonstrate that combining culture-dependent and culture-independent approaches enhances the sensitivity of either approach alone. Our techniques were able to cultivate 43 of the 48 families detected by deep sequencing; the five families recovered solely by culture-independent approaches were all present at very low abundance (<0.002% total reads). 46% of the molecular signatures detected by culture from the six patients were only identified in an anaerobic environment, suggesting that a large proportion of the cultured airway community is composed of obligate anaerobes. Most significantly, using 20 growth conditions per specimen, half of which included anaerobic cultivation and extended incubation times we demonstrate that the majority of bacteria present can be cultured